Rotary joints are employed with rotating heat exchanger drums as commonly used in the manufacture of paper wherein steam is introduced into a rotary drum and the condensate removed therefrom, or cooling water is circulated through the drum. Rotary joints permit the fluid medium to communicate with fixed conduit systems and be circulated through the dynamic heat exchanger.
Rotary joints often include an elongated nipple which is concentrically affixed to the drum shaft or journal in communication with the drum interior and the joint body or housing is mounted upon the nipple for relative rotation thereto, the body being fixed and communicating with stationary supply and drainage conduit systems, and seals and bearings are interposed between the nipple and body to maintain the interrelationship between these components for producing a fluid-tight relationship therebetween. Examples of rotary joints developed by the assignee are shown in U.S. Pat. Nos. 3,594,019 and 4,262,940.
As the seals within the rotary joint body are subjected to the pressure of the fluid therein, such pressure often imposes a force on the seal which increases the pressure at the seal face thereby accelerating wear and increasing the torque requirements for rotating the nipple relative to the body. Various types of compensating structure has been proposed for reducing seal wear due to internal pressures such as shown in assignee's U.S. Pat. Nos. 2,700,558 and 3,874,707. However, the structure of the joints shown in such patents do not completely eliminate the seal wear problems due to internal fluid pressures.
It is an object of the invention to provide a rotary joint particularly suitable for use with higher pressure, temperature and speed installations wherein the joint is relatively economical to manufacture and assemble, and may be readily serviced.
Another object of the invention is to provide a rotary joint employing a rotating nipple having a joint body mounted thereon wherein seals interposed between the nipple and body are mounted upon an enlarged portion of the nipple and are of such a configuration as to be substantially balanced with respect to the influence of the fluid pressures being imposed thereon to reduce seal wear and operating torque requirements.
A further object of the invention is to provide a rotary joint utilizing a relatively rotating nipple and body wherein a pair of substantially balanced seals are mounted upon the nipple and are biased in opposite axial directions against seal faces defined on the body.
An additional object of the invention is to provide a rotary joint utilizing a relatively rotating nipple and body wherein axially displaceable seals mounted upon the nipple within the body are substantially balanced and biased in opposite axial directions against seal faces formed on the body and alignment bushings interposed between the nipple and body prevent radial displacement between these components.
Another object of the invention is to provide a rotary joint utilizing a relatively rotating nipple and body wherein opposed axially displaceable seals mounted upon the nipple engage body sealing faces and during seal wear relative axial displacement of the body and nipple is prevented permitting syphon pipe structure mounted within the nipple to be truly static and free of axial displacement during seal wear.
In the practice of the invention, an elongated tubular nipple is attached concentrically to the end of the dryer drum shaft in a known manner. The nipple includes an enlarged central region located between cylindrical regions of lesser diametrical dimension and the enlarged portion includes a radially extending flange and a diametrical portion on each axial side of the flange upon which annular seals are located for axial displacement on the nipple in opposite directions.
A stationary body circumscribes the nipple defining a chamber in which the nipple enlarged portion is located. An inlet port is defined in the body communicating with the chamber, and radial orifices formed in the enlarged portion of the nipple establish communication between the body chamber and nipple bore.
The ends of the body are enclosed by annular plates which circumscribe the nipple. A wear plate is removably bolted to the side of the body disposed toward the heat exchanging drum, while an assembly plate is bolted to the outer side of the body. Each of these plates include an annular alignment bushing or bearing engaging reduced diameter portions of the nipple wherein a concentric radial relationship between the nipple and body will be maintained during installation and provide radial orientation between the nipple and body during operation.
The inner radial surfaces of the wear and assembly plates constitute flat seal faces each engaged by an annular carbon seal mounted upon opposite axial sides of the nipple flange and sealed with respect to the nipple cylindrical surfaces upon which they are mounted, but the seals are capable of axial displacement on these surfaces. Each seal includes a first annular pressure face disposed adjacent the nipple flange, and each seal includes a radial annular shoulder facing its associated body plate forming a second pressure face wherein the forces imposed upon the pressure faces of each seal by the fluid medium are in opposed axial direction and tend to balance each other with respect to seal axial displacement. The area of the first seal faces adjacent the flange is slightly greater than the shoulder area of the second seal faces disposed toward the associated body plate whereby a slightly greater force is imposed upon the seal toward the associated plate to assure effective fluid-tight sealing. The seals are keyed to the nipple flange by dowel pins which prevent rotation of the seals on the nipple, but permit axial displacement as seal wear occurs.
The nipple extends completely through the joint body permitting spaced axial engagement between the nipple and body by alignment bushings providing resistance to relative bending forces as well as radial orientation, and as the wear occurring in the seals does not result in relative axial displacement between the nipple and body the axial orientation of the nipple and body remains constant throughout the life of the rotary joint and this relationship is of particular advantage when a drum syphon pipe is located within the nipple and sealed with respect thereto. This "fixed" relationship of the body provides superior sealing between the syphon pipe and nipple throughout the joint life. When a syphon pipe is used with the nipple, a conduit fitting component, such as an elbow, is mounted upon the body in communication with the outer end of the nipple and syphon pipe.